The object of this study is to relate the presence of multiple hemoglobins in adult red cells to their sites of biosynthesis in erythroid marrow cells at various stages of their maturation. Chain separation and analyses of the chains of the different rat hemoglobins will yield information concerning chemical differences. Separation of marrow erythroid cells by the method of thin layer counter-current distribution will yield cells of various ages whose hemoglobins will be identified. Examination of two major hemoglobins in the adult red cells of the guinea pig is being carried out in order to determine whether the phenomenon of non-uniform biosynthesis of multiple hemoglobin in various kinds of erythroid cells is a general phenomenon.